In a ferroelectric capacitor used for a ferroelectric memory and the like, it is known that an oblique orientation (<111>, <222> etc.) of a capacitor film (a LiTaO3 film, Pb (Zr, Ti) O3 (PZT) film etc.) becomes strong so that a capacitor characteristic improves. Conventionally, the improvement of orientation is intended by optimizations of a film forming condition of the capacitor film itself or an annealing condition, however, in recent years, a method of improving the orientation more effectively is required.
With respect to such request, it is known that the stronger a c-axis orientation becomes, the stronger the oblique orientation of the capacitor becomes in a crystal orientation of a bottom electrode of the ferroelectric capacitor having a planar structure, and a method of intensifying the c-axis orientation of the bottom electrode is being considered.
Concerning an Al wiring used in various kinds of semiconductor devices, a base metal film is formed in order to improve a migration endurance, and a high orientation for the film as well as a thicker film are required for acquiring a high effect.
As materials for the bottom electrode and the base metal film, refractory metal films such as Ti, Ta and the like are chiefly used, which are formed, in general, by a DC magnetron sputtering method and so on. In addition, for the improvement of the c-axis orientation of the base metal film, there exist a method of mixing moisture with sputtering gas (Ar gas).
However, when a Ti film is formed by the DC magnetron sputtering method, the orientation of Ti sometimes fluctuate, depending on an ultimate vacuum of a film forming chamber and a processing lot number.
Sufficient orientation can not be obtained by merely mixing the moisture with the sputtering gas. And further, if the moisture adheres to a jig of a film forming chamber, the moisture causes an abnormal discharge (arc-plasma), as a result, the discharge is not stabilized and a hillock or a foreign substance sometimes occur. In addition, oxygen in the moisture remains for a long time, and the oxidation of the base metal film is possibly brought about. As a result, problems such as a peeling and the increase of resistance happen to occur, which contrarily cause the decrease of migration.
Non-Patent Document 1
“Preferred Orientation in Ti Films Sputter-Deposited on SiO2 Glass: The Role of Water Chemisorption on the Substrate” by Oowaki et al, in Japanese Journal of Applied Physics issued on 1 Feb. 1997, vol. 36, p. L154-L157.